Date published
It has been recently recognised that an error has been incorporated in the Scotland-specific modelling of background and roadside NO2 maps for 2009, 2010, 2015 and 2020 that were published on the Scottish Air Quality database in March 2011.
Maps of estimated annual mean NO2 concentrations were calculated from modelled NOX concentrations using a calibrated version of the updated oxidant-partitioning model (Jenkins, 2004; Murrells et al., 2008). This model uses representative equations to account for the chemical coupling of NO, NO2, and O3 within the atmosphere. The modelled background and roadside NO2 concentration is calculated from background or roadside NOX concentration using a sixth order polynomial relationship of the form:
NO2 = a[NOX] + a2[NOX]2 + a3[NOX]3 + ... + ai[NOX]i x [OX]B + c ,
where:
i = 6,
NO2 = background or roadside NO2 concentration (ppb),
[NOX] = background or roadside NOX concentration (ppb),
[OX]B = background oxidant concentration (ppb),
abc = coefficients.
For the background NO2 model coefficients a1 and c are calculated by comparing the measured NOX to the ratio of the [NO2]obs/[NO2]calc, whilst for the roadside NO2 model coefficients a1, a2 and c are calculated by comparing the measured NOX to the ratio of the [NO2]obs/[NO2]calc. In both cases, these coefficients were incorrectly derived in the original Scotland-specific modelling published in March 2011. The coefficients have been revised and background and roadside NO2 concentrations for 2009 have subsequently been re-calculated and new maps prepared. Corrected maps of background NO2 concentrations for future years (2010, 2015, and 2020) have also been produced.
All of the corrected maps are now available at:
http://www.scottishairquality.co.uk/data/mapping
The Scotland-specific background maps of NOx and PM10 published in March 2011 are not affected by this error.
Maps of estimated annual mean NO2 concentrations were calculated from modelled NOX concentrations using a calibrated version of the updated oxidant-partitioning model (Jenkins, 2004; Murrells et al., 2008). This model uses representative equations to account for the chemical coupling of NO, NO2, and O3 within the atmosphere. The modelled background and roadside NO2 concentration is calculated from background or roadside NOX concentration using a sixth order polynomial relationship of the form:
NO2 = a[NOX] + a2[NOX]2 + a3[NOX]3 + ... + ai[NOX]i x [OX]B + c ,
where:
i = 6,
NO2 = background or roadside NO2 concentration (ppb),
[NOX] = background or roadside NOX concentration (ppb),
[OX]B = background oxidant concentration (ppb),
abc = coefficients.
For the background NO2 model coefficients a1 and c are calculated by comparing the measured NOX to the ratio of the [NO2]obs/[NO2]calc, whilst for the roadside NO2 model coefficients a1, a2 and c are calculated by comparing the measured NOX to the ratio of the [NO2]obs/[NO2]calc. In both cases, these coefficients were incorrectly derived in the original Scotland-specific modelling published in March 2011. The coefficients have been revised and background and roadside NO2 concentrations for 2009 have subsequently been re-calculated and new maps prepared. Corrected maps of background NO2 concentrations for future years (2010, 2015, and 2020) have also been produced.
All of the corrected maps are now available at:
http://www.scottishairquality.co.uk/data/mapping
The Scotland-specific background maps of NOx and PM10 published in March 2011 are not affected by this error.